Check the recommended resolution/refresh rate for your monitor, and keep it at that. Most LCD's are optimised for 60Hz, even though they may display higher resolutions. Also try changing your color depth to 32-bit and see if that helps. It probably won't, but it's worth a try.
I've been thinking about replacing my current S775 motherboard and processor with something newer since my motherboard can't support enough RAM to run Carmageddon: Reincarnation properly.
Since Intel's processors have barely had any performance enhancements since Sandy Bridge, I'm considering buying a used Z68 motherboard and an i5 2500k from eBay. It'd only cost half as much as buying a new system (Z87, 4670k), and would only be less than 10% slower. Do you guys think this is a good idea?